Update README.

Author: chengpeiquan

README.md

@@ -70,7 +70,7 @@ Tips: Please remember to turn off the debug mode before publish.
 
 You can install the plugin from NPM.
 
-```
+```bash
 npm install vue-cnzz-analytics --save-dev
 ```
 

README.zh-CN.md

@@ -68,7 +68,7 @@ isDebug|否|boolean|是否开启 debug 模式，默认 `false`，开启后会在
 
 方式一：通过 NPM 安装
 
-```
+```bash
 npm install vue-cnzz-analytics --save-dev
 ```